Corrosion back on the process safety agenda

Pipeline corrosion has moved back up the process safety agenda after the US Chemical Safety Board(CSB) identified the issue as a key factor in the vapor cloud release and massive fire that occurred at the Chevron refinery on 6 August, 2012.

A CSB investigation team concluded that Chevron had, for 10 years, failed to effectively apply inherently safer design principles and upgrade piping in its crude oil processing unit that was extremely corroded and ultimately ruptured to cause a release of hydrocarbons that endangered 19 workers and caused a major fire.

It is already well known that fouling and corrosion can threaten the reliability and safety of critical atmospheric fractionator overhead condensing systems. These problems often can impair production, raise maintenance costs and reduce profits.

Meanwhile, another driver behind the need for greater corrosion control is a push by refiners around the world turn to lower-cost "opportunity" crude oil feedstocks and aim to maximize middle distillate production.

Among the companies responding to these issues is GE, which has introduced TrueSense for Process, an online crude overhead monitoring system (COMS) that continuously monitors, applies and optimises the delivery of chemicals into the crude process stream to control corrosion.

Episodic pH variations in the overhead of the crude unit that are measured in the condensate water are often missed. This is mainly because spot testing is performed manually due to the lack of online, reliable data-gathering devices that can make adjustments to corrosion control chemistry in real time.

TrueSense for Process-COMS detects these pH variations quickly and rapidly minimizes their effects. Because undetected events can produce very high short-term corrosion, such a fast response helps to avoid unscheduled shutdowns, reduce maintenance expenses and improve profitability and operational flexibility.